The present invention relates to a method and apparatus for removing seeds from a standing crop without cutting the crop. The invention also relates to an apparatus for separating seeds from an air stream.
It is often desirable to harvest seeds from many varieties of plants, for example grasses, for the purposes of repropagation. In particular it is desirable to harvest seeds from such grasses as common meadow foxtail, Garrisons Creeping Foxtail, broom, crested wheat and timothy.
Many varieties of grass seed are difficult to harvest. Such factors as small seed size, light weight of the seeds, the presence of chaff material associated with the seeds, loose attachment of the seed to the plant, variable seed head height, varying rates of seed maturation, and weeds in the grass crop, all contribute to the problems in harvesting grass seed.
Conventional swathing and combining equipment designed to cut, swath, thresh and clean cereal grain crops have been used to harvest grass seed. However, the grass seed is not successfully harvested by this equipment. If such conventional equipment is used, a harvest of about 50% grass seed and 50% chaff, stem, leaf, and weed material is recovered. This mixture is very difficult, if not impossible, to clean or plant, mainly due to its poor flow characteristics.
Furthermore, the conventional swathing and combining equipment cannot selectively recover the mature seeds from the grass plant, since the entire crop must be cut at one time. Only the seeds which are mature at that time are useful. A considerable amount of the mature grass seed is lost in this harvesting procedure, both from shattering of the seed heads by the wind, from impacting of the seed head by the swather reel's bats, and by falling out of the swath left to dry in the field. Also, the late-maturing seeds are effectively lost.
To overcome some of these problems, seed harvesters have been designed to harvest grass seed from the standing crop without cutting the crop. One prior art device of this type was developed by R. W. Whitney, R. M. Ahring and C. M. Taliaferro and is described in Transactions of the ASAE, 1979, page 270. The device is essentially a modification of a grain swather unit, from which the cutting bar has been removed. The device includes a generally horizontal platform which is moved through the crop just below the height of the seed heads. A rotating reel above the platform is used to bend the plant rearwardly over the platform. A plurality of flexible flails are fixed to the reel. A stationary concave plate is mounted horizontally on the platform. On rotation of the reel the seed heads are trapped between the flails and the concave plate to strip the seeds from the plant. The seeds are pulled by suction into a screen-type air-seed separator.
While this device may overcome some of the above-mentioned problems, it is believed to have its difficulties. By pulling the plant stem rearwardly over the forwardly advancing horizontal platform, a substantial amount of stem breakage can take place. The broken stems, together with the seed heads, are then harvested with the seeds. Further, it is believed that the rotating reel, in order to strip the seeds, must be rotated at a relatively high speed. The reel would then cause significant seed dislodging as the reel flails impacted the seed heads ahead of the horizontal platform. Also, in running the reel at this high speed, considerable air turbulence would be generated, which in turn would scatter the seed.
Other seed harvesters have been described in the patent literature for harvesting seeds from standing crops; see for example U.S. Pat. No. 2,460,029 issued to R. M. Ramp and U.S. Pat. No. 2,046,932 issued to F. Wyatt et al.
The Ramp device was designed specifically for the harvesting of dandelion seeds and is not believed to be suitable for the harvest of other seeds such as grass seeds. The device consists of two parallel brushes rotating in opposite directions, one brush being mounted above and ahead of the other, across an opening. Air is drawn through the opening. The brushes are arranged to whisk the seeds from the plant. The seeds are then pulled between the brushes into the opening. The seeds are separated from the air in a screen-type air-seed separator. It is believed that the rotating brushes trap dandelion fluff between the brush bristles and thereby whisk the seeds from the plant. Most seeds, especially grass seeds, cannot be dislodged from the plant by this action. It is believed that a more positive stripping action is necessary. Also, the upper brush in the Ramp device is shown to include a large diameter central hub, around which the brushes are fixed. In grass crops this hub would cause substantial undesirable bending and breakage of the stems and seeds heads.
The harvesting device of Wyatt et al was designed specifically to strip clover heads from standing clover plants. The clover head is pinched off as the bats of a rotating reel contact a stationary flexible strip. The clover head is pulled by an air stream into a combined screen and cyclone type separator. This device is not able to strip the clover seed directly from the clover plant. The device therefore includes a cylinder-concave arrangement to thresh the seeds from the harvested clover heads.
With respect to the air-seed separating devices, screen-type and cyclone-type separators have been used in seed harvesters. The screen-type separators often become clogged as the seeds, and any stem or chaff material, blind the screen surface. The cyclone-type separators usually need to be quite large to effect seed-air separation. The separator is then heavy, cumbersome and costly to carry around the field.
In summary, there is a need for a seed harvester having the following desirable capabilities:
(1) the ability to strip seeds from a standing crop without cutting the crop;
(2) the ability to preferentially strip mature seeds from a standing crop, leaving the immature seeds on the plant for subsequent maturing and harvesting;
(3) the ability to strip seeds from a standing crop without causing substantial stem breakage by bending of the stems or seed loss from impacting of the seed heads; and
(4) provision for seed-air separation in a compact arrangement which can be economically carried around the field.